1. Field of the Invention
The invention relates to intravenous delivery systems and in particular to ambulatory intravenous delivery systems which provide a metered flow while allowing the patient to move about.
2. Background Art
In current medical technology, there exists a variety of devices that deliver intravenous fluids and chemotherapy to patients. Some of these devices offer some degree of portability, however, the majority of these devices confine a patient to bed. Portable or so called "ambulatory" devices usually work on an infusion pump delivery principle. That is, a system which pumps the substance into the patient to overcome the resistance of patient pressure. The system is operated without actual flow measurement being fed back into the system therefore the control available in these devices is greatly limited. These devices in most cases place a minimum of importance on patient comfort and convenience.
Normally, the various infusion pump systems that generate their own pressure to overcome the resistance of patient pressure do not contain means for controlling fluid flow at the various pressures required. The common stationary gravity feed units provide limited control possibilities by altering the height of the container above the patient, but this requires an apparatus upon which to hang the container. Such an apparatus greatly limits portability of the unit.
The known volumetric peristaltic or piston-cylinder pumps have large power requirements and therefore require frequent battery replacement. Higher viscosity fluids such as hyperalimintation solutions are limited to use with these devices and races lower than 100 ml/hr.
In "unmonitored" units, that is units where the flow rate is not checked against the requested flow rate, poorly regulated or uneven flow may be disastrous. In the unmonitored type of unit, the flow rate is easily affected by such factors as tubing position, patient arm height or arm orientation.
Thus, while various systems are known for providing intravenous delivery of fluids to a patient, there is no single system that allows the patient to be ambulatory in and out of a hospital and where the device can deliver larger quantities of fluid such as 500 ml/hr at various pressures, maintaining precisely controlled rates, or even as low as 10 ml/hr, with a minimum of battery power, control feedback and maximum possible comfort for the patient.